Marine propulsion



March 23, 1943.

MARINE PROPULS ION Filed Jan. 16, 1941 A. RIETZKE 2,314,370

Patented Mar. 23, 1943 MARINE PROPULSION ns Corners, N. J., assignor,

August Rietzke, Gordo by mesne assignment tion, Mercer County,

New Jersey s, to Bow Arch Corpora- N. J., a corporation of Application January 16, 1941, Serial No. 374,759 3 Claims. (Cl. 115-37) mounted with respect to the rudder of the boat .to assure the boat to continue to travelstraight ahead in the event either of the propellers should become ineffective.

Another object of the invention is to provide a means of this kind wherein the propellers are positioned at predetermined points forward of and to opposite sides of the rudder post whereby the wash from each of the propellers is caused to strike the rudder blade at substantially the center thereof so that when one of the propellers should become ineffective, the boat will continue to travel straight ahead.

An additional object of the invention is to provide a marine propulsion wherein twin screws are employed and wherein the axes of rotation of the propellers are in convergence toward the center of frictional resistance on the surface of the hull of the ship, and also wherein each of the propellers is positioned ahead or in advance of the rudder post a distance equal to the distance between the axial center of both of the propellers, said centers of the propellers, of course, being alined in a direction at right angles to the center line of the boat, and wherein said propellers each has its axial center positioned to one side of the center line of the hull a distance equal to one-half of the distance from the center line of the hull to a point on the water line directly above the propeller.

In the drawing:

Fig. 1 is a diagrammatic view in top plan illustrating a marine propulsion assembled and arlranged in accordance with an embodiment of my invention.

Fig. 2 is a diagramm tic view in side elevation having indicated thereon certain lines whereby Y is computed the location of a propeller.

Fig. 3 is a diagrammatic View taken substantially on the line 3-3of Fig. 1.

Fig. 4 is a diagrammatic view taken of the stern. v

Fig. 5 is an elevational view of a diagrammatic character of the rudderas herein comprised.

While the accompanying drawing particularly illustrates the invention in connection with a surface traveling boat and the following description is based thereon, it is to be understood that the same principles as herein embodied can be employed to the same advantage in connection with aircraft and under which circumstances the positioning of the propellers will be reverse to what is herein described and illustrated.4

The present embodiment vof the invention is kbased upon a boat structure wherein the center line of the hull I-I at the water line isv50 feet and the distance over the outside surface of the hull from the keel line to the water line at the greatest breadth of the hull H is 7 feet. It is to be stated at this time that in referring to lengths, the full-length is given, but in referring to a breadth, only a half width is given, which is in accordance with the'agreed rules of naval architects.

The propellers P rotate upon axes which forwardly converge toward the center line of the hull at the point CR or frictional resistance of the water upon the submerged surface of the hull when the bo-at is traveling at a predetermined rate of speed. These propellers P are also so positioned at opposite sides of the center line of the boat and at such points forwardly of the rudder post to assure the inner portion of the wash from each of the propellers, as indicated at 2, to strike the adjacent surface of the rudder blade B at substantially the center thereof. This striking of the wash upon each surface of the rudder blade B is to occur when said blade B is in straight ahead position or within a variation of not over 10.

The propellers P are positioned forwardly from the rudder post a distance substantially equal to the distance between the axes of rotation of the propellers and each of said propellers has its axes of rotation to one side of the center line of the boat a distance equal to substantially onehalf of the distance between the center line of the boat and the water line directly above the propeller. This particular location of each of the propellers P with respect to the blade B, and the diversion of the axes of the propellers with respect to the center line (GLOB) of the hull constitutes the essential feature of the present invention as by this particular assembly, the boat will be caused to continue to travel'straight ahead in the event either of the-propellers P should become ineffective due to the fact that the action of the wash from the working propeller upon the central portion of the rudder blade B will resist the tendency of the hull H to swing under the action of the one operating propeller.

By wash vis meant the water between the slip stream and the hull and which water or wash moves at a greater speed.

In the accompanying drawing, the following lines denote the following:

AB=distance over'the outside surface of the hull from water line to keel line at the bow.

BCT-distance over the outside surface of the hull from keel line to water line at greatest breadth of the submerged hull.

PLIF=Fig. 2, distance over the outside surface of the hull from forward stem or bow at water line to greatest breadth of hull at water line,

FE=distance over the outside surface of the hull from keel to Water line at the stern of the boat.

PLIA, Fig. 2=distance over the outside surface of the hull at the water line from the greatest breadth of hull to stern of boat at Water line.

To establish the center of resistance l, thedistance AB and the distance BC, as indicated in Fig. 3, are added and the resultant .sum .is divided by 2. The quotient obtained is multiplied by the distance PLIF, Fig. 2. Then there is added the distance BC, Fig. 3, and the distance FE, Fig. 4. This total is divided by Zand the quotient multiplied by the distance PLIA, Fig. .2. The rst product is subtracted from the second product and this remainder is divided -by 2 and the quotient divided by the distance CB, Fig. 3, the product'of which is added to distance PEI F, Fig. 1, which will be the center of resistance CR, Fig. 1, in feet from the bow of theboat along the keel line.

Assuming the distance (AB) vover the outside surface of the hull from waterline lto Ykeel line at the bow is 2 feet and the distance (BC) over the outside surface of the hull from keel line to'water line at greatest breadth or" the submerged hull is 7-feet, the total oi AB and `iC'will'be 9 feet. Dividing this 9 feet .by 2 gives 4.5 feet. Presuming the distance (PLiF) over the outside 'surfaceof the hull from forward stem or bowat water -line to greatest breadth of'hull at water line is 2l feet, this dimension PLiF is multiplied by 4.5 which gives 94.5 sq. ft. Presurning the distance (FE) over the outside surface of the hull from keel to water line at the stern of the boat is 5 ft., this dimension is added to the'7 it. (BC) Fig. 3. rI'he resultant sum ci 12 is 'divided by 2, givinglG ft. This 6 ft. is multiplied by 28, the distance (PIAA) Fig. 2, over the outside surface of the hull at Athe water line from the greatest breadth of hull to stern of boat at water line, giving 168 sq..ft. The 94.5 sq. ft. hereinbeiore noted is subtracted from the 168 sq. it., giving a remainder of .73.5 sq. it. This 73.5 is divided by 2,giving ka result of.36.75. This 36.75 is divided by '7 (BC) Fig. 3, whichas hereinbefore stated, is the distance over the outside surface of the hull from keel line to water line at greatest breadth of the submerged hull. This gives a quotient oi 5.25 ft., which is tobe added to 21 ft., which is the distance (FIAF) Fig. l, from forward stem or bowat-water` iineto greatest'breadth of hull at water line. The total 26.25 is the distance of the icenter of .irictional resistance (CR) from the bow at the centerline of boat (GLOB).

The additional lines denote the following:

BiWe-the point ofthe water line at the bow.

SlVV=the point of the water line at the stern.

ACzgreatest breadth in feet of boat at water line.

COR=center of rudder post.

CR=center of resistance.

COS=the point which controls the determination of the angle of the axis of the propeller.

CLOB=the center line of boat.

WL=water line.

To determine the position ofshaftgthe 'length of boat in feet at Water line between BSW Vand SIW, which has hereinbefcre been stated as 50 feet..is divided by 6 which is the presumed distance AC, which is the greatestbreadth in feet of boat at water line, which is 8.33 feet. There is then laid olf aline 8.33 inches from'the center line ofthe boat at the keel line' at the center of the :rudder post (COR) and at rightanglesrto said center line of the boat. The outer end of this line constitutes a point COS which is the point which controls the determination of the angle of the axis of the propeller. It is to be particularly noted that the length of this line in inches is of .a number equal to the number of feet resulting by the dividing by 6 the distance between BSW and SIW which, as hereinbefore stated, is the length of the boat at the water line. The axis of rotation .of a propeller P is in parallelism with an imaginary line at the point COS to the center of resistance CR. The true position of the Apropeller is half the distance on a line between the imaginary line connecting the point CR and COS and the water line between BIW and SIW and forwardly of the center of the rudder COR a distance equal to `the full length'of the vline from COS to the Water line (WL) and at right'angles to the-center line of boat (CLOB).

The rudder area is 1 square inch to 1 square foot of submerged surface of hull and the area'of the balance of the rudder should be 1/3 of thearea of lthe rudder blade. The depth Yof the rudder shouid be calculated with `respect vto the draft-of the boat amidship.

The foregoing calculations' are based kon boats of l'hfp. to 2 square feet or" submerged resistance up to '75 feet in length and are effective in a lee- .way of lill/2% above or below. For each 36% power increase to the square foot of submerged surfaceofhull and .increase of length of hull, the degree of angleof theaxes or the propellers with respect to the center line (GLOB) of the hull shouldbe advanced 1.

'Whatis claimed is:

1. .'Ihe combination with a hull of a boatand a .rudder `at one end portion thereof; of propellers at :oppositevsides o1" the center line of the boat y ahead of the rudder, the axes of the propellers converging toward the bow, said .axes being outwardly ofzand inparallelism with imaginary Ylines A'from ythe center of frictional resistancepn ,the surfaceof the hull to points aligned in a direction at rightangles to the centerline of 4thehull at the rudder pest. each point beingspa-ced from said .center line of the hull at the rudder post ininches -a Ydistance determined by the quotient resulting from dividing the distance in feet over the outside surface of the hull yat the .waterlineifrorn the bow to the stern of .thehull by tone-half .of the greatest breadth in feet of the thi/ill ,at-fthe y'water line, the axial centers of the propellers .being alinedin'a direction at right angles'to the center line of the hull, each propeller being positioned such a distance to one side of thecenterdine of the 'boat as kto-cause the Washof thefipropeller to strikethe blade of the rudder.

2. The combination with a hull of a boatand a rudder at one vend portion thereof; of propellers at opposite sides of :the center line of :the boat ahead of the rudder, the axes of thepropellers converging toward the bow, said axes being outwardly of and in parallelism with imaginarylines from the center of frictional resistanceon the surface of the hull to points alignedin a direction atright angles to the center line of the hull at the rudderpost, each point being spaced from said center line of the hull at the rudder post in inches a distance determined by the quotient resulting from dividing the distance in feet over theoutside surface `of the hullV at the water line from the bow'to the stern of the hull by one-half of the greatest breadth in feet ofthe hull at the water line, the Vaxial centers of the propellers being alined in a direction at right anglesto the center line of the hull, each propeller being positioned such a distance to one side of the center line of the boat to cause the wash of the propeller to strike the blade of the rudder, the propellers being positioned forwardly from the rudder post a disl tance substantially equal to the distance between the axes'of the propellers, and each of said pro-1f pellers having its axis to one side of the center line of the boat a distance equal to substantially one-half of the distance between the center line of the boat and the water line directly above the propeller.

3. The combination with a hull of a boat and a rudder at one end portion thereof; of propellers at opposite sides of the center line of the boat ahead of the rudder, the axes of the propellers converging toward the bow, said axes being outwardly of and in parallelism with imaginary lines from the center of frictionalresistance on the surface of the hull to points aligned in a direction at right angles to the center line of the hull at the rudder post, each point being spaced from said center line of the hull at the rudder post in inches a distance determined by the quotient resulting from dividing the distance in feet over the outside surface of the hull at the water line from the bow to the stern of the hull by one-half of the greatest breadth in feet of the hull at the water line, the axial centers of the Propellers being alined in a direction at right angles to the center line of the hull, each propeller being positioned such a distance to one side of the center line of the boat to cause the wash of the propeller to strike the blade of the rudder, thegpropellers being positioned forwardly from the rudder post a distance substantially equal to the distance between the axes of the propellers, and each of said propellers having its axis to one side of the center line of the -boat a distance equal tf'o substantially one-half of the distance between'fythe center line of the boat and the water line directly above the propeller, said axial centers of the propellers being alined in a direction at right angles to the center line of the boat.

AUGUST RIETZKE. 

